Concrete is now a favoured construction material, not just of engineers but of architects and designers. Aesthetically, concrete has come to be recognised for its robust and solid appearance with designers now experimenting more with its textures and finishes, however, neglecting the colour potential of concrete is mainly due to the cost associated with using pigments. The cost of colouring concrete with existing pigments such as carbon black , synthetics [2, 3], haematite and various oxides can result in up to a doubling of material costs, when compared to that of ordinary concrete. This cost is even greater if colours such as blue are requested as the cobalt required to achieve this colour can be of great expense. One possible low cost, sustainable solution for pigmenting concrete is the use of recycled toner. Recycling, as required by law  is usually well-organised and efficient, but the toner powder removed from spent cartridges is degraded, hence not suitable for the use in printers any more. It is a very fine material, typically polymer based with various other compounds such as iron oxide, amorphous silica and pigment, is immiscible in water and poses a dust hazard and so far the main disposal route is landfilling in closed containers.
University of Dundee
DD1 4HN, Schottland, UK